1. Field of Invention
The present invention relates to screwdrivers and more particularly to such a screwdriver having a revolving cylinder containing replaceable screwdriver tips with improved characteristics.
2. Related Art
A conventional screwdriver having a revolving cylinder containing replaceable screwdriver tips is shown in FIGS. 1, 2, and 3. The screwdriver comprises a body 1, a handle 2, a revolving cylinder 3, and a shell 4. The body 1 comprises a space 11 having a slot 12, a ratchet wheel 13 in a forward end, a sleeve 14 extended forwardly from the ratchet wheel 13, a rear guide tube 15 having a plurality of dents 16, a pipe 17 extended through the guide tube 15 and the space 11, and a cylinder 18 put on the pipe 17. A magnet 25 is provided proximate a front end of the sleeve 14. The revolving cylinder 3 comprises an end projection 31 having a plurality of holes 32 for containing a plurality of screwdriver tips A, an annular flange 33 in the intermediate portion, and a plurality of grooves 34 equally spaced around the other end. The shell 4 comprises two halves 41 formed together by electron-beam welding with the revolving cylinder 3 enclosed therein. Each half 41 comprises a bottom recess 42 with the projection 31 received therein, a spring 43 and a steel ball 44 provided on the recess 42, a half circular trough 45 with the flange 33 received therein, a half circular opening 46 on the bottom such that a screwdriver tip A is able to access through the a complete circular opening 46, a sliding block 47 on an underside adapted to slide in the slot 12 such that a shank 21 is adapted to pass the hole 32 to retain the revolving cylinder 3 in the space 11. In use, a user may turn the revolving cylinder 3 to select a desired screwdriver tip A. Once selected, push the handle 2 forward to project the screwdriver tip A from a front end of the sleeve 14. Thus, the user can insert the screwdriver tip A in a slot in the head of a screw.
But this is unsatisfactory for the purpose for which the invention is concerned for the following reasons:                (a) The shank 21 may clear both the revolving cylinder 3 and the shell 4. Thus, both the revolving cylinder 3 and the shell 4 tend to fall on the ground due to no fastening.        (b) Two halves 41 of the shell 4 are formed together by electron-beam welding with the revolving cylinder 3 enclosed therein. Thus, the shell 4 must be replaced together if only revolving cylinder 3 is required to replace. This inevitably increases the manufacturing cost. In addition, the forming of the shell 4 with the revolving cylinder 3 enclosed therein is a time consuming process.        (c) Forming of a steel ball 22, a spring 23, and a cap 24 on a front end of the handle 2 and the forming of the dents 16 in which one of the dents 16 is adapted to receive the spring biased steel ball 22 for positioning is a time consuming process of assembly.        (d) Forming of the grooves 34 equally spaced around the other end of the revolving cylinder 3 and the associated spring 43 and the steel ball 44 positioned in one of the grooves 34 is a time consuming process of assembly. Thus, the need for improvement still exists.        